Rare sleep disorder linked to smoking, pesticides

June 29, 2012

Smoking, head injury, pesticide exposure and farming are risk factors for a rare sleep disorder that causes people to act out their dreams occasionally causing bodily harm¯according to new research. The disorder, known as Rapid Eye Movement Sleep Behaviour (RBD) disorder, is often a precursor to neurodegenerative diseases, such as Parkinson’s disease and dementia. The new study, led by Dr. Ronald Postuma of the Research Institute of the McGill University Health Centre (RI-MUHC), is published in the online issue of Neurology®.

RBD is characterized by the absence of muscle paralysis normally present during sleep. Without the muscle paralysis, a wide spectrum of behavioural release can occur during the REM (rapid eye movement) stage of slumber when our most vivid dreaming occurs. This can range from simple limb twitches to more complex movements, which can even be violent in nature and in some cases result in injury to either the person with RBD or their bed partner. RBD is estimated to occur in only 0.5 per cent of adults, but studies have shown that more than 50 per cent of people with the disorder develop a neurodegenerative disease.

To overcome issues of limited sample size, Dr. Postuma and his colleagues enlisted the support of the International REM Sleep Behaviour Disorder Study Group (RBDSG), which enabled them to access data from 13 institutions in 10 countries. Using a standardized questionnaire that assessed potential environmental and lifestyle risk factors, 347 people with REM sleep behavior disorder were compared to 347 people who did not have the disorder.

The study revealed that people with RBD were 59 per cent more likely to have had a previous head injury with loss of consciousness, 67 per cent more likely to have worked as farmers, and more than twice as likely to have been exposed to pesticides through work. Those with the disorder also had fewer years of education, with an average of 11.1 years, compared to 12.7 years for those without the disorder.

“Until now, we didn’t know much about the risk factors for this disorder, except that it was more common in men and in the elderly,” says Dr. Postuma, who is also a professor of medicine in the department of neurology and neurosurgery at McGill University. “We will now be able to look at ways to intervene with the neurodegenerative process in patients with this disorder. They are the ideal candidates for trial therapies because they are at the earliest stages of neurological degeneration.”